Sahih Al Bukhari Hadith Number 1094

Narrated Jabir bin `Abdullah: The Prophet (peace be upon him) used to offer the Nawafil, while riding, facing a direction other than that of the Qibla.

18  Shortening the Prayers (At-Taqseer)
Hadith number 1094
Volume no 2
Chapter: 7 (To offer Nawafil on the back of animals)